Stator for rotating electric machine

ABSTRACT

A stator includes a stator core having slots, a stator coil comprised of three phase windings, phase busbars each electrically connecting a corresponding one of the phase windings to an inverter, and a neutral busbar star-connecting the phase windings to define a neutral point therebetween. In each of the slots of the stator core, there are arranged K in-slot portions of the phase windings of the stator coil in K layers so as to be radially aligned with each other, where K is an even number. The phase and neutral busbars are electrically connected with those in-slot portions of the phase windings of the stator coil which are arranged at the radially outermost layer or the radially innermost layer in the respective slots of the stator core so as to be circumferentially spaced from one another by M slot-pitches or more, where M is a slot multiplier number.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. patent application Ser. No.15/225,305, filed Aug. 1, 2016, which claims priority from JapanesePatent Application No. 2015-152831 filed on Jul. 31, 2015, the contentof which is hereby incorporated by reference in its entirety into thisapplication.

BACKGROUND 1 Technical Field

The present invention relates to stators for rotating electric machinesthat are used in, for example, motor vehicles as electric motors andelectric generators.

2 Description of Related Art

There are known rotating electric machines that are used in motorvehicles as electric motors and electric generators. These rotatingelectric machines generally include a rotor and a stator. The rotor isrotatably provided and functions as a field. The stator is disposed inradial opposition to the rotor and functions as an armature.

Japanese Patent Application Publication No. JP2013162636A discloses astator for a rotating electric machine. The stator is formed byassembling a plurality of stator pieces into an annular shape. Each ofthe stator pieces includes a coil that is formed by winding an electricconductor wire around a bobbin, and a stator core having teeth to whichthe coil is mounted. Moreover, in the patent document, there is alsodisclosed a power distribution component that is designed to reduce thenumber of types of connection terminals connecting busbars and the coilsof the stator, thereby reducing the manufacturing cost.

There are also known two methods of winding a coil on a stator core,namely, concentrated winding and distributed winding. Concentratedwinding is a winding method in which the coil is wound so as to beconcentrated in one slot of the stator core, as disclosed in the abovepatent document. On the other hand, distributed winding is a windingmethod in which the coil is wound so as to be distributed to a pluralityof slots of the stator core.

Compared to concentrated winding, distributed winding is moreadvantageous in terms of torque improvement and noise reduction.However, at the same time, distributed winding has a disadvantage suchthat the distance between each circumferentially-adjacent pair of theslots of the stator core is short. Therefore, in the case of joininglead wires to power and neutral wires by welding, the distance betweeneach circumferentially-adjacent pair of the resultant welds isaccordingly short; the lead wires are led out from a coil end part of astator coil which protrudes from an axial end face of the stator core.Consequently, creeping discharge may occur between the welds, resultingin insulation failure.

SUMMARY

According to one aspect of the present invention, there is provided astator for a rotating electric machine. The stator includes an annularstator core, a three-phase stator coil, a plurality of phase connectingmembers and a neutral connecting member. The stator core has a pluralityof slots arranged in a circumferential direction thereof. The statorcoil is comprised of three phase windings that are mounted on the statorcore so as to be different in electrical phase from each other. Each ofthe phase windings includes a plurality of in-slot portions each ofwhich is received in one of the slots of the stator core. Each of thephase connecting members is provided to electrically connect acorresponding one of the phase windings of the stator coil to anexternal electrical device. The neutral connecting member is provided tostar-connect the phase windings of the stator coil to define a neutralpoint therebetween. In each of the slots of the stator core, there arearranged K of the in-slot portions of the phase windings of the statorcoil in K layers so as to be radially aligned with each other, where Kis an even number. The number of the slots formed in the stator core permagnetic pole of a rotor of the rotating electric machine and per phaseof the stator coil is set to M, where M is a natural number greater thanor equal to 2. Each of the phase windings of the stator coil iscomprised of a plurality of sub-windings that are connected parallel toeach other. For each of the sub-windings, the in-slot portion of thesub-winding which is arranged at the Nth layer in one of the slots ofthe stator core is electrically connected with the in-slot portion ofthe sub-winding which is arranged at the (N+1)th layer in another one ofthe slots, where N is a natural number greater than or equal to 1 andless than K. The phase connecting members and the neutral connectingmember are electrically connected with those in-slot portions of thephase windings of the stator coil which are arranged at a radiallyoutermost layer or a radially innermost layer in the respective slots ofthe stator core so as to be circumferentially spaced from one another byM slot-pitches or more.

With the above configuration, it becomes possible to arrange electricaljoints formed between the phase and neutral connecting members and thephase windings of the stator coil so as to be circumferentially spacedfrom one another by M slot-pitches or more. Consequently, it becomespossible to secure sufficient creepage distances between the electricaljoints, thereby preventing creeping discharge from occurringtherebetween. As a result, it becomes possible to improve the insulationproperties of the stator.

According to another aspect of the present invention, there is provideda stator for a rotating electric machine. The stator includes an annularstator core and a stator coil. The stator core has a plurality of slotsarranged in a circumferential direction thereof. The stator coil iscomprised of a plurality of phase windings that are distributedly woundon the stator core. Each of the phase windings includes a plurality ofin-slot portions each of which is received in one of the slots of thestator core. The stator coil has an annular coil end part protrudingfrom an axial end face of the stator core. There are electrical jointsformed for making electrical connection of the stator coil and coveredby an electrically-insulative resin covering member. The electricaljoints are located axially outside the coil end part of the stator coil.The stator coil includes a plurality of bridging wires each of whichelectrically connects one pair of the in-slot portions of the phasewindings of the stator coil respectively received in two different onesof the slots of the stator core. The bridging wires are located axiallyoutside the coil end part of the stator coil and radially inside theelectrical joints. Each of the bridging wires has a pair ofaxially-extending portions and a circumferentially-extending portionbetween the pair of axially-extending portions. The bridging wires arearranged so that the circumferentially-extending portions of thebridging wires overlap one another over an entire circumferential rangeof the coil end part of the stator coil.

With the above arrangement, during rotation of a rotor of the rotatingelectric machine, cooling air (or coolant) that flows in the centrifugaldirection of the rotor is blocked by the bridging wires; thus, theelectrical joints are prevented from being directly exposed to the flowof the cooling air. Consequently, it becomes possible to reduce thermalstress induced by uneven temperature in the electrical joints, therebypreventing breakage of the electrical joints. As a result, it becomespossible to improve the insulation properties of the stator.

According to yet another aspect of the present invention, there isprovided a stator for a rotating electric machine. The stator includesan annular stator core, a three-phase stator coil, a plurality of phaseconnecting members and a neutral connecting member. The stator core hasa plurality of slots arranged in a circumferential direction thereof.The stator coil is comprised of three phase windings that are mounted onthe stator core so as to be different in electrical phase from eachother. Each of the phase connecting members is provided to electricallyconnect a corresponding one of the phase windings of the stator coil toan external electrical device. The neutral connecting member is providedto star-connect the phase windings of the stator coil to define aneutral point therebetween. The stator coil has an annular coil end partprotruding from an axial end face of the stator core. The phase andneutral connecting members are located axially outside the stator coreand radially outside the coil end part of the stator coil. The phase andneutral connecting members are arranged in axial alignment with eachother. Among the phase and neutral connecting members, the neutralconnecting member is located closest to the stator core.

With the above arrangement, it becomes possible to reduce the potentialdifference to ground, thereby preventing occurrence of a ground fault.As a result, it becomes possible to improve the insulation properties ofthe stator.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given hereinafter and from the accompanying drawings ofexemplary embodiments, which, however, should not be taken to limit theinvention to the specific embodiments but are for the purpose ofexplanation and understanding only.

In the accompanying drawings:

FIG. 1 is a partially cross-sectional view, taken along an axialdirection, of a rotating electric machine which includes a statoraccording to a first embodiment;

FIG. 2 is a perspective view of a stator of the rotating electricmachine;

FIG. 3 is a perspective view of part of the stator including a firstcoil end part of a stator coil of the stator;

FIG. 4 is a perspective view of a pair of large and small electricconductor segments used for forming the stator coil;

FIG. 5 is a schematic front view of part of the pair of large and smallelectric conductor segments;

FIG. 6 is a cross-sectional view illustrating the configuration of theelectric conductor segments used for forming the stator coil;

FIG. 7 is a schematic cross-sectional view illustrating the arrangementof the electric conductor segments in the first coil end part of thestator coil;

FIG. 8 is a perspective view showing part of the first coil end part ofthe stator coil;

FIG. 9 is a schematic view illustrating the arrangement of apex parts ofturn portions of the large electric conductor segments in the first coilend part of the stator coil;

FIG. 10 is a schematic view illustrating the cooling air flow throughthe apex parts of the turn portions of the large electric conductorsegments in the first coil end part of the stator coil;

FIG. 11 is a schematic view illustrating the cooling air flow throughapex parts of turn portions of the small electric conductor segments inthe first coil end part of the stator coil;

FIG. 12 is a schematic circuit diagram of the stator coil;

FIG. 13 is a schematic view illustrating the configuration of each ofsub-windings of phase windings of the stator coil;

FIG. 14 is a schematic view illustrating the arrangement of a U-phasewinding of the stator coil;

FIG. 15 is a schematic view illustrating only the arrangement of a firstsub-winding U1 of the U-phase winding;

FIG. 16 is a schematic view illustrating only the arrangement of asecond sub-winding U2 of the U-phase winding;

FIG. 17 is a schematic view illustrating only the arrangement of a thirdsub-winding U3 of the U-phase winding;

FIG. 18 is a schematic view illustrating only the arrangement of afourth sub-winding U4 of the U-phase winding;

FIG. 19 is a schematic view illustrating only the arrangement of a fifthsub-winding U5 of the U-phase winding;

FIG. 20 is a schematic view illustrating the arrangement of thesub-windings U1-U5 of the U-phase winding in pairs of U-phase slots Aand B of a stator core of the stator;

FIG. 21 is a schematic view showing the number of in-slot portions ofeach of the sub-windings U1-U5 of the U-phase winding arranged at eachof first to sixth layers in the U-phase slots A and B;

FIG. 22 is a schematic cross-sectional view illustrating the arrangementof terminal-side and neutral point-side winding sections of thesub-windings of the phase windings of the stator coil;

FIG. 23 is a schematic axial view illustrating the arrangement of theterminal-side and neutral point-side winding sections;

FIG. 24 is an axial end view illustrating the arrangement of theterminal-side and neutral point-side winding sections;

FIG. 25 is another axial end view illustrating the arrangement of theterminal-side and neutral point-side winding sections;

FIG. 26 is a schematic cross-sectional view illustrating the arrangementof phase and neutral busbars;

FIG. 27 is a schematic view illustrating the electric current density ofthe U-phase busbar;

FIG. 28 is a schematic view illustrating the electric current density ofthe neutral busbar;

FIG. 29 is a side view of part of the stator before electrical jointsare covered by a resin covering member;

FIG. 30 is a side view of part of the stator after the electrical jointsare covered by the resin covering member;

FIG. 31 is a schematic cross-sectional view illustrating the arrangementof bridging wires of the stator coil;

FIG. 32 is a perspective view of the bridging wires;

FIG. 33 is a perspective view showing part of the bridging wires throughenlargement;

FIG. 34 is a schematic cross-sectional view illustrating the arrangementof a pair of electric conductor wires forming one electrical joint;

FIG. 35 is a schematic cross-sectional view showing the electrical jointof FIG. 34 through enlargement;

FIG. 36 is a perspective view of a stator according to a secondembodiment;

FIG. 37 is a schematic cross-sectional view illustrating the integrationof busbars by a resin member in the stator according to the secondembodiment;

FIG. 38 is a cross-sectional view illustrating a first modification ofthe second embodiment;

FIG. 39 is a cross-sectional view illustrating a second modification ofthe second embodiment;

FIG. 40 is a cross-sectional view illustrating a third modification ofthe second embodiment; and

FIG. 41 is a cross-sectional view illustrating a fourth modification ofthe second embodiment.

DESCRIPTION OF EMBODIMENTS

Exemplary embodiments and their modifications will be describedhereinafter with reference to FIGS. 1-41. It should be noted that forthe sake of clarity and understanding, identical components havingidentical functions throughout the whole description have been marked,where possible, with the same reference numerals in each of the figuresand that for the sake of avoiding redundancy, descriptions of theidentical components will not be repeated.

First Embodiment

FIG. 1 shows the overall configuration of a rotating electric machine 1according to a first embodiment.

The rotating electric machine 1 is designed to be used in a motorvehicle, such as a passenger car or truck, as an electric motor.

As shown in FIG. 1, the rotating electric machine 1 includes a housing10, a rotor 14 and a stator 20. The housing 10 is comprised of a pair ofcup-shaped housing pieces 10 a and 10 b which are jointed together atthe open ends thereof. The housing 10 has a pair of bearings 11 and 12mounted therein, via which a rotating shaft 13 is rotatably supported bythe housing 10. The rotor 14 is received in the housing 10 and fixed onthe rotating shaft 13. The stator 20 is fixed in the housing 10 so as tosurround the radially outer periphery of the rotor 14.

The rotor 14 has a plurality of permanent magnets embedded atpredetermined positions therein. The permanent magnets form a pluralityof magnetic poles on the radially outer periphery of the rotor 14 facingthe radially inner periphery of the stator 20. The magnetic poles arearranged in the circumferential direction of the rotor 14 atpredetermined intervals so that the polarities of the magnetic polesalternate between north and south in the circumferential direction. Thenumber of the magnetic poles can be suitably set according to the designspecification of the rotating electric machine 1. In the presentembodiment, the number of the magnetic poles is set to be equal to, forexample, 10 (i.e., 5 north poles and 5 south poles).

Referring now to FIGS. 2 and 3, the stator 20 includes: an annular (orhollow cylindrical) stator core 30 having a plurality of slots 31arranged in the circumferential direction thereof; a three-phase statorcoil 40 comprised of a U-phase winding 41U, a V-phase winding 41V and aW-phase winding 41W that are distributedly wave-wound on the stator core30 so as to be received in the slots 31 of the stator core 30 and bedifferent in electrical phase from each other; a U-phase busbar 61, aV-phase busbar 62 and a W-phase busbar 63 respectively electricallyconnecting the U-phase, V-phase and W-phase windings 41U, 41V and 41W ofthe stator coil 40 to an inverter (not shown); and a neutral busbar 64electrically connecting the U-phase, V-phase and W-phase windings 41U,41V and 41W of the stator coil 40 to define a neutral pointtherebetween. In addition, the U-phase, V-phase and W-phase busbars 61,62 and 63 respectively correspond to U-phase, V-phase and W-phaseconnecting members while the neutral busbar 64 corresponds to a neutralconnecting member.

In the present embodiment, the stator core 30 is formed by laminating aplurality of annular magnetic steel sheets in the axial direction of thestator core 30 and fixing them together by, for example, staking. Inaddition, between each adjacent pair of the magnetic steel sheets, thereis interposed an insulating film. It should be appreciated that otherconventional metal sheets may also be used instead of the magnetic steelsheets.

Moreover, as shown in FIGS. 2 and 3, the stator core 30 includes anannular back core 33 and a plurality of stator teeth 34 in addition tothe aforementioned slots 31. The stator teeth 34 each extend radiallyinward from the back core 33 and are circumferentially spaced at apredetermined pitch. Each of the slots 31 is formed between onecircumferentially-adjacent pair of the stator teeth 34. Accordingly, theslots 31 are circumferentially arranged at the same predetermined pitchas the stator teeth 34. Moreover, each of the slots 31 extends in theaxial direction of the stator core 30 so as to axially penetrate thestator core 30 and opens on the radially inner surface of the statorcore 30. In addition, for each of the slots 31, the depth direction ofthe slot 31 coincides with a radial direction of the stator core 30.

In the stator core 30, there are formed M slots 31 per magnetic pole ofthe rotor 14 that has the ten magnetic poles and per phase of thethree-phase stator coil 40. Here, M represents a slot multiplier numberwhich is a natural number greater than or equal to 2. In the presentembodiment, the slot multiplier number M is set to be equal to 2.Accordingly, the total number of the slots 31 formed in the stator core30 is equal to 60 (i.e., 2×10×3).

The U-phase, V-phase and W-phase windings 41U, 41V and 41W of the statorcoil 40 are star-connected (or Y-connected) with each other (see FIG.12). Each of the U-phase, V-phase and W-phase windings 41U, 41V and 41Wincludes a plurality of in-slot portions 51C and a plurality of turnportions 52A and 52B. Each of the in-slot portions 51C is received inone of the slots 31 of the stator core 30. Each of the turn portions 52Aand 52B is located outside the slots 31 of the stator core 30 andconnects one pair of the in-slot portions 51C respectively received intwo different ones of the slots 31.

In the present embodiment, the stator coil 40 is formed by: (1)inserting a plurality of substantially U-shaped electric conductorsegments 50 into the slots 31 of the stator core 30 from a first axialside (i.e., the upper side in FIG. 2) of the stator core 30; (2)twisting free end parts of each of the electric conductor segments 50,which protrude outside the slots 31 of the stator core 30 on a secondaxial side (i.e., the lower side in FIG. 2) of the stator core 30,respectively toward opposite circumferential sides; and (3) joining eachcorresponding pair of distal ends of the twisted free end parts of allthe electric conductor segments 50 by, for example, welding.Consequently, all the electric conductor segments 50 are electricallyconnected in a predetermined pattern, forming the stator coil 40.

Furthermore, in the present embodiment, as shown in FIG. 4, the electricconductor segments 50 forming the stator coil 40 are comprised of aplurality of large electric conductor segments 50A and a plurality ofsmall electric conductor segments 50B that have a smaller size than thelarge electric conductor segments 50A. The large and small electricconductor segments 50A and 50B are formed by press-shaping an electricconductor wire, which has a substantially rectangular cross section,into the substantially U-shape using shaping dies. It should be notedthat the shaping dies used for forming the large electric conductorsegments 50A are different from those used for forming the smallelectric conductor segments 50B.

Each of the large electric conductor segments 50A has a pair of straightportions 51A extending parallel to each other and a turn portion 52Athat connects ends of the straight portions 51A on the same side. On theother hand, each of the small electric conductor segments 50B has a pairof straight portions 51B extending parallel to each other and a turnportion 52B that connects ends of the straight portions 51B on the sameside. The turn portions 52B of the small electric conductor segments 50Bhave a smaller length than the turn portions 52A of the large electricconductor segments 50A.

More specifically, in the present embodiment, the turn portions 52A ofthe large electric conductor segments 50A are formed to have acircumferential length of seven slot-pitches. On the other hand, theturn portions 52B of the small electric conductor segments 50B areformed to have a circumferential length of five slot-pitches.Consequently, it becomes possible to arrange the large and smallelectric conductor segments 50A and 50B so that each of the turnportions 52A of the large electric conductor segments 50A is locatedaxially outside and overlaps one of the turn portions 52B of the smallelectric conductor segments 50B. Accordingly, the turn portions 52A ofthe large electric conductor segments 50A may be referred to as outerturn portions 52A; the turn portions 52B of the small electric conductorsegments 50B may be referred to as inner turn portions 52B.

Moreover, each of the turn portions 52A of the large electric conductorsegments 50A includes an apex part 53A that is positioned at the centerof the turn portion 52A in the extending direction of the turn portion52A (or in the circumferential direction of the stator core 30) andfurthest in the turn portion 52A from a first axial end face 30 a of thestator core 30; the first axial end face 30 a is on the first axial sideof the stator core 30. The apex part 53A extends in the circumferentialdirection of the stator core 30 and parallel to the first axial end face30 a of the stator core 30. Further, at the circumferential center ofthe apex part 53A, there is formed, by press-shaping, a crank-shapedpart 54A that is bent to radially offset the apex part 53A. The amountof radial offset realized by the crank-shaped part 54A is set to besubstantially equal to the radial thickness of the large and smallelectric conductor segments 50A and 50B. Similarly, each of the turnportions 52B of the small electric conductor segments 50B includes anapex part 53B that is positioned at the center of the turn portion 52Bin the extending direction of the turn portion 52B (or in thecircumferential direction of the stator core 30) and furthest in theturn portion 52B from the first axial end face 30 a of the stator core30. The apex part 53B extends in the circumferential direction of thestator core 30 and parallel to the first axial end face 30 a of thestator core 30. Further, at the circumferential center of the apex part53B, there is formed, by press-shaping, a crank-shaped part 54B that isbent to radially offset the apex part 53B. The amount of radial offsetrealized by the crank-shaped part 54B is also set to be substantiallyequal to the radial thickness of the large and small electric conductorsegments 50A and 50B.

In the present embodiment, as shown in FIG. 5, the circumferentiallength L1 of each of the outer apex parts 53A (i.e., the apex parts 53Aof the turn portions 52A of the large electric conductor segments 50A)is set to be greater than the circumferential length L2 of each of theinner apex parts 53B (i.e., the apex parts 53B of the turn portions 52Bof the small electric conductor segments 50B) by a predetermined amount.In addition, the outer apex parts 53A are located axially outside theinner apex parts 53B.

Moreover, in the present embodiment, as shown in FIGS. 4 and 8, thebending direction of the crank-shaped parts 54A formed in the outer apexparts 53A is opposite to the bending direction of the crank-shaped parts54B formed in the inner apex parts 53B.

More specifically, in FIG. 8, for each of the outer apex parts 53A, thecrank-shaped part 54A formed in the outer apex part 53A is bent from aright end portion of the outer apex part 53A radially outward (i.e., ina direction into the plane of FIG. 8), so that a left end portion of theouter apex part 53A is located radially outside the right end portion.In contrast, for each of the inner apex parts 53B, the crank-shaped part54B formed in the inner apex part 53B is bent from a right end portionof the inner apex part 53B radially inward (i.e., in a direction out ofthe plane of FIG. 8), so that a left end portion of the inner apex part53B is located radially inside the right end portion.

Consequently, for each of the outer apex parts 53A, the left end portionof the outer apex part 53A is offset, by the crank-shaped part 54Aformed in the outer apex part 53A, from the right end portion of theouter apex part 53A radially outward (i.e., in the direction into theplane of FIG. 8). In contrast, for each of the inner apex parts 53B, theleft end portion of the inner apex part 53B is offset, by thecrank-shaped part 54B formed in the inner apex part 53B, from the rightend portion of the inner apex part 53B radially inward (i.e., in thedirection out of the plane of FIG. 8).

That is, in the present embodiment, the direction of radial offset ofthe outer apex parts 53A by the respective crank-shaped parts 54A isopposite to the direction of radial offset of the inner apex parts 53Bby the respective crank-shaped parts 54B.

Moreover, in the present embodiment, as shown in FIGS. 9-11, all of theinclination angles θ of the crank-shaped parts 54A and 54B formed in therespective outer and inner apex parts 53A and 53B to the circumferentialdirection of the stator core 30 are set to be equal to each other.

Furthermore, referring back to FIGS. 4 and 5, each of the turn portions52A of the large electric conductor segments 50A also includes a pair ofoblique parts 55A that are respectively formed on oppositecircumferential sides of the apex part 53A so as to extend obliquelywith respect to the first axial end face 30 a of the stator core 30 at afirst predetermined oblique angle α1. Each of the turn portions 52A ofthe large electric conductor segments 50A further includes a pair ofbent parts 56A. Each of the bent parts 56A is formed, by press-shapingusing shaping dies, between one of the oblique parts 55A and one of thestraight portions 51A connected by the turn portion 52A. The bent parts56A protrude from the first axial end face 30 a of the stator core 30.Similarly, each of the turn portions 52B of the small electric conductorsegments 50B also includes a pair of oblique parts 55B that arerespectively formed on opposite circumferential sides of the apex part53B so as to extend obliquely with respect to the first axial end face30 a of the stator core 30 at a second predetermined oblique angle α2.Each of the turn portions 52B of the small electric conductor segments50B further includes a pair of bent parts 56B. Each of the bent parts56B is formed, by press-shaping using shaping dies, between one of theoblique parts 55B and one of the straight portions 51B connected by theturn portion 52B. The bent parts 56B protrude from the first axial endface 30 a of the stator core 30. In addition, in the present embodiment,the first predetermined oblique angle α1 and the second predeterminedoblique angle α2 are set to be equal to each other (see FIG. 5).

In the present embodiment, as shown in FIG. 6, each of the large andsmall electric conductor segments 50A and 50B is configured with anelectric conductor 58 and an insulating coat 59 that covers the outersurface of the electric conductor 58. The electric conductor 58 is made,for example, of an electrically-conductive metal (e.g., copper) and hasa substantially rectangular cross section. The insulating coat 59 ismade, for example, of an electrically-insulative resin.

Moreover, in the present embodiment, as shown in FIG. 7, each of thelarge and small electric conductor segments 50A and 50B forming thestator coil 40 is arranged so that a pair of side faces of the electricconductor segment, which correspond to the longer sides of thesubstantially rectangular cross section of the electric conductorsegment, face in the radial direction of the stator core 30.

Referring back to FIG. 2, the stator coil 40 has an annular first coilend part 40 a on the first axial side (i.e., the upper side in FIG. 2)of the stator core 30 and an annular second coil end part 40 b on thesecond axial side (i.e., the lower side in FIG. 2) of the stator core30. The first coil end part 40 a is constituted of the turn portions 52Aand 52B of the large and small electric conductor segments 50A and 50Bwhich protrude from the first axial end face 30 a of the stator core 30.The second coil end part 40 b is constituted of the twisted free endparts of the large and small electric conductor segments 50A and 50Bwhich protrude from the second axial end face 30 a of the stator core30.

In the present embodiment, as shown in FIG. 8, the first coil end part40 a of the stator coil 40 has a two-layer structure such that for eachcircumferentially-adjacent pair of the turn portions 52A of the largeelectric conductor segments 50A and the turn portions 52B of the smallelectric conductor segments 50B, the apex parts 53A and 53B of the pairof the turn portions 52A and 52B axially overlap each other. That is,the turn portions 52A of the large electric conductor segments 50A,which are located on the axially outer side, together form an outerlayer of the first coil end part 40 a of the stator coil 40; the turnportions 52B of the small electric conductor segments 50B, which arelocated on the axially inner side, together constitute an inner layer ofthe first coil end part 40 a. In addition, as described previously, thebending direction of the crank-shaped parts 54A formed in the apex parts53A of the turn portions 52A of the large electric conductor segments50A is opposite to the bending direction of the crank-shaped parts 54Bformed in the apex parts 53B of the turn portions 52B of the smallelectric conductor segments 50B.

Moreover, as shown in FIG. 9, with all of the inclination angles θ ofthe crank-shaped parts 54A set to be equal to each other, eachradially-facing pair of the crank-shaped parts 54A formed in therespective outer apex parts 53A extend parallel to each other keeping aradial space S therebetween. Further, for each of the outer apex parts53A, the crank-shaped part 54A formed in the outer apex part 53A isinclined, at the inclination angle θ to an imaginary line Y which isperpendicular to a radially-extending imaginary line X, so that onecircumferential end (i.e., the left end in FIG. 9) of the crank-shapedpart 54A is located radially outward (i.e., upward in FIG. 9) of theother circumferential end (i.e., the right end in FIG. 9) of thecrank-shaped part 54A. Consequently, as shown in FIG. 10, duringrotation of the rotor 14 in a counterclockwise direction as indicated byan arrow a in FIG. 10, cooling air will flow from the radially inside tothe radially outside of the first coil end part 40 a of the stator coil40 through the spaces formed between radially-facing pairs of the outerapex parts 53A in the outer layer of the first coil end part 40 a. As aresult, it is possible to secure the cooling performance of the rotatingelectric machine 1 when the rotor 14 rotates in the counterclockwisedirection a.

Similarly, though not shown in the figures, with all of the inclinationangles θ of the crank-shaped parts 54B set to be equal to each other,each radially-facing pair of the crank-shaped parts 54B formed in therespective inner apex parts 53B extend parallel to each other keeping aradial space S therebetween. However, the bending direction of thecrank-shaped parts 54B formed in the respective inner apex parts 53B isopposite to the bending direction of the crank-shaped parts 54A formedin the respective outer apex parts 53A. Consequently, as shown in FIG.11, during rotation of the rotor 14 in a clockwise direction asindicated by an arrow b in FIG. 11, cooling air will flow from theradially inside to the radially outside of the first coil end part 40 aof the stator coil 40 through the spaces formed between radially-facingpairs of the inner apex parts 53B in the inner layer of the first coilend part 40 a. As a result, it is also possible to secure the coolingperformance of the rotating electric machine 1 when the rotor 14 rotatesin the clockwise direction b.

In the present embodiment, as shown in FIG. 12, the U-phase, V-phase andW-phase windings 41U, 41V and 41W of the stator coil 40, which arestar-connected with each other, are each comprised of a plurality (e.g.,five in the present embodiment) of sub-windings that are connectedparallel to each other.

Specifically, the U-phase winding 41U is comprised of sub-windings U1,U2, U3, U4 and U5 that are connected parallel to each other. The V-phasewinding 41V is comprised of sub-windings V1, V2, V3, V4 and V5 that areconnected parallel to each other. The W-phase winding 41W is comprisedof sub-windings W1, W2, W3, W4 and W5 that are connected parallel toeach other.

Moreover, in the present embodiment, as shown in FIG. 13, each of thesub-windings U1-U5, V1-V5 and W1-W5 of the phase windings 41U-41W of thestator coil 40 is configured to include: a terminal-side winding section42 (more specifically, corresponding one of 42U1-42U5, 42V1-42V5 and42W1-42W5) electrically connected to a corresponding one of the U-phase,V-phase and W-phase busbars 61, 62 and 63; a neutral point-side windingsection 43 (more specifically, corresponding one of 43U1-43U5, 43V1-43V5and 43W1-43W5) electrically connected to the neutral busbar 64; and amain winding section 44 (more specifically, corresponding one of44U1-44U5, 44V1-44V5 and 44W1-44W5) between the terminal-side andneutral point-side winding sections 42 and 43. The terminal-side windingsection 42 forms a terminal-side lead wire of the sub-winding, while theneutral point-side winding section 43 forms a neutral point-side leadwire of the sub-winding.

Specifically, taking only the sub-winding U1 of the U-phase winding 41Uas an example, the sub-winding U1 is configured to include: aterminal-side winding section 42U1 electrically connected to the U-phasebusbar 61; a neutral point-side winding section 43U1 electricallyconnected to the neutral busbar 64; and a main winding section 44U1between the terminal-side and neutral point-side winding sections 42U1and 43U1. The terminal-side winding section 42U1 forms a terminal-sidelead wire of the sub-winding U1, while the neutral point-side windingsection 43U1 forms a neutral point-side lead wire of the sub-winding U1.

In addition, for the sake of convenience of explanation, hereinafter,the terminal-side winding sections 42U1-42U5 of the sub-windings U1-U5of the U-phase winding 41U will also be simply referred to as theterminal-side winding sections 42U of the U-phase winding 41U; theneutral point-side winding sections 43U1-43U5 of the sub-windings U1-U5of the U-phase winding 41U will also be simply referred to as theneutral point-side winding sections 43U of the U-phase winding 41U; andthe main winding sections 44U1-44U5 of the sub-windings U1-U5 of theU-phase winding 41U will also be simply referred to as the main windingsections 44U of the U-phase winding 41U. Similarly, the terminal-sidewinding sections 42V1-42V5 of the sub-windings V1-V5 of the V-phasewinding 41V will also be simply referred to as the terminal-side windingsections 42V of the V-phase winding 41V; the neutral point-side windingsections 43V1-43V5 of the sub-windings V1-V5 of the V-phase winding 41Vwill also be simply referred to as the neutral point-side windingsections 43V of the V-phase winding 41V; and the main winding sections44V1-44V5 of the sub-windings V1-V5 of the V-phase winding 41V will alsobe simply referred to as the main winding sections 44V of the V-phasewinding 41V. The terminal-side winding sections 42W1-42W5 of thesub-windings W1-W5 of the W-phase winding 41W will also be simplyreferred to as the terminal-side winding sections 42W of the W-phasewinding 41W; the neutral point-side winding sections 43W1-43W5 of thesub-windings W1-W5 of the W-phase winding 41W will also be simplyreferred to as the neutral point-side winding sections 43W of theW-phase winding 41W; and the main winding sections 44W1-44W5 of thesub-windings W1-W5 of the W-phase winding 41W will also be simplyreferred to as the main winding sections 44W of the W-phase winding 41W.

In the present embodiment, the U-phase, V-phase and W-phase windings41U, 41V and 41W of the stator coil 40 are arranged in the slots 31 ofthe stator core 30 in the same manner. Therefore, for the sake ofavoiding redundancy, only the arrangement of the U-phase winding 41U inthe slots 31 of the stator core 30 will be described hereinafter withreference to FIGS. 14-21.

FIG. 14 illustrates, among the three phase windings 41U-41W of thestator coil 40, only the U-phase winding 41U arranged in the slots 31 ofthe stator core 30. FIG. 15 illustrates, among the five sub-windingsU1-U5 of the U-phase winding 41U, only the first sub-winding U1 arrangedin the slots 31 of the stator core 30. FIG. 16 illustrates, among thefive sub-windings U1-U5 of the U-phase winding 41U, only the secondsub-winding U2 arranged in the slots 31 of the stator core 30. FIG. 17illustrates, among the five sub-windings U1-U5 of the U-phase winding41U, only the third sub-winding U3 arranged in the slots 31 of thestator core 30. FIG. 18 illustrates, among the five sub-windings U1-U5of the U-phase winding 41U, only the fourth sub-winding U4 arranged inthe slots 31 of the stator core 30. FIG. 19 illustrates, among the fivesub-windings U1-U5 of the U-phase winding 41U, only the fifthsub-winding U5 arranged in the slots 31 of the stator core 30.

In the present embodiment, as mentioned previously, the number of themagnetic poles formed in the rotor 14 by the permanent magnets is equalto 10. Moreover, during operation of the rotating electric machine 1,magnetic flux, which is generated by the rotor 14 and passes through thestator 20, forms a plurality of magnetic poles in the stator 20. Thenumber of the magnetic poles formed in the stator 20 is also equal to10, corresponding to the number of the magnetic poles of the rotor 14.That is, the number of the magnetic poles formed in the stator 20 is amultiple of the number of sub-windings of the U-phase winding 41U, morespecifically the least common multiple of 2 and the number ofsub-windings of the U-phase winding 41U (i.e., 2×5=10).

In FIGS. 14-19, let the magnetic pole located at twelve o'clock be thefirst pole and the remaining magnetic poles respectively be the secondto the tenth poles counting in the clockwise direction. Moreover, inFIGS. 14-19, the electrical connection between the in-slot portions 51Cof the U-phase winding 41U on the first coil end part 40 a side (i.e.,on the first axial side of the stator core 30) are shown with continuouslines while the electrical connection between the in-slot portions 51Cof the U-phase winding 41U on the second coil end part 40 b side (i.e.,on the second axial side of the stator core 30) are shown with dashedlines.

In the present embodiment, the in-slot portions 51C of the U-phasewinding 41C are received in ten pairs of the slots 31 of the stator core30. Hereinafter, for the sake of convenience of explanation, these tenpairs of the slots 31 will be referred to as ten pairs of U-phase slotsA and B. For each of the ten pairs, the two U-phase slots A and B of thepair are circumferentially adjacent to each other. Moreover, since theslot multiplier number M is set to 2, the ten pairs of the U-phase slotsA and B are circumferentially spaced at six slot-pitches. That is, theU-phase slots A are circumferentially spaced from one another at sixslot-pitches; the U-phase slots B are circumferentially spaced from oneanother at six slot-pitches.

Furthermore, in the present embodiment, in each of the U-phase slots Aand B, there are received six of the in-slot portions 51C of the U-phasewinding 41U in radial alignment with each other (see FIG. 14). In otherwords, in each of the U-phase slots A and B, there are received thein-slot portions 51C of the U-phase winding 41U in six layers.Hereinafter, the six layers will be sequentially referred to as thefirst, second, . . . , fifth and sixth layers from the radially innerside to the radially outer side. In addition, for each of thesub-windings U1-U5 of the U-phase winding 41U, the in-slot portions 51Cof the sub-winding will be sequentially referred to as the first,second, . . . , 23rd and 24th in-slot portions from the winding startside to the winding finish side.

First, referring to FIG. 15, the arrangement of the 24 in-slot portionsof the first sub-winding U1 of the U-phase winding 41U in the ten pairsof the U-phase slots A and B will be described.

The first in-slot portion of the sub-winding U1 is arranged at the sixthlayer (i.e., the radially outermost layer) in the U-phase slot B of thefirst pole. The second in-slot portion of the sub-winding U1 is arrangedat the fifth layer in the U-phase slot B of the second pole; the U-phaseslot B of the second pole is away from the U-phase slot B of the firstpole by six slot-pitches in the clockwise direction.

In addition, the first in-slot portion of the sub-winding U1 is includedin the terminal-side winding section 42U1 of the sub-winding U1. Awinding start-side end of the terminal-side winding section 42U1 isextended to the first coil end part 40 a side (i.e., the front side ofFIG. 15), forming the terminal-side lead wire of the sub-winding U1.

The third in-slot portion of the sub-winding U1 is arranged at the sixthlayer in the U-phase slot A of the third pole; the U-phase slot A of thethird pole is away from the U-phase slot B of the second pole by fiveslot-pitches in the clockwise direction. The fourth in-slot portion ofthe sub-winding U1 is arranged at the fifth layer in the U-phase slot Aof the fourth pole; the U-phase slot A of the fourth pole is away fromthe U-phase slot A of the third pole by six slot-pitches in theclockwise direction.

The fifth in-slot portion of the sub-winding U1 is arranged at thefourth layer in the U-phase slot B of the fifth pole; the U-phase slot Bof the fifth pole is away from the U-phase slot A of the fourth pole byseven slot-pitches in the clockwise direction. The sixth in-slot portionof the sub-winding U1 is arranged at the third layer in the U-phase slotB of the sixth pole; the U-phase slot B of the sixth pole is away fromthe U-phase slot B of the fifth pole by six slot-pitches in theclockwise direction.

The seventh in-slot portion of the sub-winding U1 is arranged at thefourth layer in the U-phase slot A of the seventh pole; the U-phase slotA of the seventh pole is away from the U-phase slot B of the sixth poleby five slot-pitches in the clockwise direction. The eighth in-slotportion of the sub-winding U1 is arranged at the third layer in theU-phase slot A of the eighth pole; the U-phase slot A of the eighth poleis away from the U-phase slot A of the seventh pole by six slot-pitchesin the clockwise direction.

The ninth in-slot portion of the sub-winding U1 is arranged at thesecond layer in the U-phase slot B of the ninth pole; the U-phase slot Bof the ninth pole is away from the U-phase slot A of the eighth pole byseven slot-pitches in the clockwise direction. The tenth in-slot portionof the sub-winding U1 is arranged at the first layer in the U-phase slotB of the tenth pole; the U-phase slot B of the tenth pole is away fromthe U-phase slot B of the ninth pole by six slot-pitches in theclockwise direction.

The eleventh in-slot portion of the sub-winding U1 is arranged at thesecond layer in the U-phase slot A of the first pole; the U-phase slot Aof the first pole is away from the U-phase slot B of the tenth pole byfive slot-pitches in the clockwise direction. The twelfth in-slotportion of the sub-winding U1 is arranged at the first layer in theU-phase slot A of the second pole; the U-phase slot A of the second poleis away from the U-phase slot A of the first pole by six slot-pitches inthe clockwise direction.

The thirteenth in-slot portion of the sub-winding U1 is arranged at thefirst layer in the U-phase slot A of the third pole; the U-phase slot Aof the third pole is away from the U-phase slot A of the second pole bysix slot-pitches in the clockwise direction. In addition, the thirteenthin-slot portion of the sub-winding U1 is connected with the twelfthin-slot portion of the sub-winding U1 via a bridging wire 45 (see FIGS.8, 32 and 33) on the first coil end part 40 a side. The fourteenthin-slot portion of the sub-winding U1 is arranged at the second layer inthe U-phase slot A of the second pole; the U-phase slot A of the secondpole is away from the U-phase slot A of the third pole by sixslot-pitches in the counterclockwise direction. That is, from thefourteenth in-slot portion, the sub-winding U1 starts to be wound backin the counterclockwise direction.

The fifteenth in-slot portion of the sub-winding U1 is arranged at thefirst layer in the U-phase slot B of the first pole; the U-phase slot Bof the first pole is away from the U-phase slot A of the second pole byfive slot-pitches in the counterclockwise direction. The sixteenthin-slot portion of the sub-winding U1 is arranged at the second layer inthe U-phase slot B of the tenth pole; the U-phase slot B of the tenthpole is away from the U-phase slot B of the first pole by sixslot-pitches in the counterclockwise direction.

The seventeenth in-slot portion of the sub-winding U1 is arranged at thethird layer in the U-phase slot A of the ninth pole; the U-phase slot Aof the ninth pole is away from the U-phase slot B of the tenth pole byseven slot-pitches in the counterclockwise direction. The eighteenthin-slot portion of the sub-winding U1 is arranged at the fourth layer inthe U-phase slot A of the eighth pole; the U-phase slot A of the eighthpole is away from the U-phase slot A of the ninth pole by sixslot-pitches in the counterclockwise direction.

The nineteenth in-slot portion of the sub-winding U1 is arranged at thethird layer in the U-phase slot B of the seventh pole; the U-phase slotB of the seventh pole is away from the U-phase slot A of the eighth poleby five slot-pitches in the counterclockwise direction. The twentiethin-slot portion of the sub-winding U1 is arranged at the fourth layer inthe U-phase slot B of the sixth pole; the U-phase slot B of the sixthpole is away from the U-phase slot B of the seventh pole by sixslot-pitches in the counterclockwise direction.

The 21st in-slot portion of the sub-winding U1 is arranged at the fifthlayer in the U-phase slot A of the fifth pole; the U-phase slot A of thefifth pole is away from the U-phase slot B of the sixth pole by sevenslot-pitches in the counterclockwise direction. The 22nd in-slot portionof the sub-winding U1 is arranged at the sixth layer in the U-phase slotA of the fourth pole; the U-phase slot A of the fourth pole is away fromthe U-phase slot A of the fifth pole by six slot-pitches in thecounterclockwise direction.

The 23rd in-slot portion of the sub-winding U1 is arranged at the fifthlayer in the U-phase slot B of the third pole; the U-phase slot B of thethird pole is away from the U-phase slot A of the fourth pole by fiveslot-pitches in the counterclockwise direction. The 24th in-slot portionof the sub-winding U1 is arranged at the sixth layer (i.e., the radiallyoutermost layer) in the U-phase slot B of the second pole; the U-phaseslot B of the second pole is away from the U-phase slot B of the thirdpole by six slot-pitches in the counterclockwise direction.

In addition, the 24th in-slot portion of the sub-winding U1 is includedin the neutral point-side winding section 43U1 of the sub-winding U1. Awinding finish-side end of the neutral point-side winding section 43U1is extended to the first coil end part 40 a side (i.e., the front sideof FIG. 15), forming the neutral point-side lead wire 43U1 of thesub-winding U1.

The sub-winding U1 is wound on the stator core 30 so that the first tothe 24th in-slot portions of the sub-winding U1 are received in the tenpairs of the U-phase slots A and B of the stator core 30 as describedabove. Moreover, as shown with the continuous lines in FIG. 15, on thefirst axial side of the stator core 30, the in-slot portions of thesub-winding U1 are connected by the outer turn portions 52A of thesub-winding U1 (i.e., the turn portions 52A of the large electricconductor segments 50A forming the sub-winding U1) and the inner turnportions 52B of the sub-winding U1 (i.e., the turn portions 52B of thesmall electric conductor segments 50B forming the sub-winding U1). Theouter turn portions 52A of the sub-winding U1 are arranged alternatelywith the inner turn portions 52B of the sub-winding U1 in thecircumferential direction of the stator core 30; the outer turn portions52A have the circumferential length of seven slot-pitches while theinner turn portions 52B have the circumferential length of fiveslot-pitches. On the other hand, as shown with the dashed lines in FIG.15, on the second axial side of the stator core 30, the in-slot portionsof the sub-winding U1 are connected by connection portions of thesub-winding U1. Each of the connection portions is constituted of onejoined-pair of the twisted free end parts of the large and smallelectric conductor segments 50A and 50B forming the sub-winding U1, andhas a circumferential length of six slot-pitches.

Next, referring to FIG. 16, the arrangement of the 24 in-slot portionsof the second sub-winding U2 of the U-phase winding 41U in the ten pairsof the U-phase slots A and B will be described.

The first in-slot portion of the sub-winding U2 is arranged at the sixthlayer in the U-phase slot B of the ninth pole. The second in-slotportion of the sub-winding U2 is arranged at the fifth layer in theU-phase slot B of the tenth pole; the U-phase slot B of the tenth poleis away from the U-phase slot B of the ninth pole by six slot-pitches inthe clockwise direction.

That is, the first and second in-slot portions of the sub-winding U2 arerespectively offset from the first and second in-slot portions of thesub-winding U1 by an offset angle of 72° in the counterclockwisedirection. Here, the offset angle of 72° is equal to the quotient of360° divided by the number of the sub-windings of the U-phase winding41U (i.e., 5 in the present embodiment).

Moreover, the third to the 24th in-slot portions of the sub-winding U2are arranged in the U-phase slots A and B of the stator core 30 so as tobe respectively offset from the third to the 24th in-slot portions ofthe sub-winding U1 by the offset angle of 72° in the counterclockwisedirection.

In addition, the first in-slot portion of the sub-winding U2 is includedin the terminal-side winding section 42U2 of the sub-winding U2, whilethe 24th in-slot portion of the sub-winding U2 is included in theneutral point-side winding section 43U2 of the sub-winding U2. Both awinding start-side end of the terminal-side winding section 42U2 and awinding finish-side end of the neutral point-side winding section 43U2are extended to the first coil end part 40 a side (i.e., the front sideof FIG. 16), respectively forming the terminal-side and neutralpoint-side lead wires of the sub-winding U2.

Next, referring to FIG. 17, the arrangement of the 24 in-slot portionsof the third sub-winding U3 of the U-phase winding 41U in the ten pairsof the U-phase slots A and B will be described.

The first in-slot portion of the sub-winding U3 is arranged at the sixthlayer in the U-phase slot B of the seventh pole. The second in-slotportion of the sub-winding U3 is arranged at the fifth layer in theU-phase slot B of the eighth pole; the U-phase slot B of the eighth poleis away from the U-phase slot B of the seventh pole by six slot-pitchesin the clockwise direction.

That is, the first and second in-slot portions of the sub-winding U3 arerespectively offset from the first and second in-slot portions of thesub-winding U2 by the offset angle of 72° in the counterclockwisedirection.

Moreover, the third to the 24th in-slot portions of the sub-winding U3are arranged in the U-phase slots A and B of the stator core 30 so as tobe respectively offset from the third to the 24th in-slot portions ofthe sub-winding U2 by the offset angle of 72° in the counterclockwisedirection.

In addition, the first in-slot portion of the sub-winding U3 is includedin the terminal-side winding section 42U3 of the sub-winding U3, whilethe 24th in-slot portion of the sub-winding U3 is included in theneutral point-side winding section 43U3 of the sub-winding U3. Both awinding start-side end of the terminal-side winding section 42U3 and awinding finish-side end of the neutral point-side winding section 43U3are extended to the first coil end part 40 a side (i.e., the front sideof FIG. 17), respectively forming the terminal-side and neutralpoint-side lead wires of the sub-winding U3.

Next, referring to FIG. 18, the arrangement of the 24 in-slot portionsof the fourth sub-winding U4 of the U-phase winding 41U in the ten pairsof the U-phase slots A and B will be described.

The first in-slot portion of the sub-winding U4 is arranged at the sixthlayer in the U-phase slot B of the fifth pole. The second in-slotportion of the sub-winding U4 is arranged at the fifth layer in theU-phase slot B of the sixth pole; the U-phase slot B of the sixth poleis away from the U-phase slot B of the fifth pole by six slot-pitches inthe clockwise direction.

That is, the first and second in-slot portions of the sub-winding U4 arerespectively offset from the first and second in-slot portions of thesub-winding U3 by the offset angle of 72° in the counterclockwisedirection.

Moreover, the third to the 24th in-slot portions of the sub-winding U4are arranged in the U-phase slots A and B of the stator core 30 so as tobe respectively offset from the third to the 24th in-slot portions ofthe sub-winding U3 by the offset angle of 72° in the counterclockwisedirection.

In addition, the first in-slot portion of the sub-winding U4 is includedin the terminal-side winding section 42U4 of the sub-winding U4, whilethe 24th in-slot portion of the sub-winding U4 is included in theneutral point-side winding section 43U4 of the sub-winding U4. Both awinding start-side end of the terminal-side winding section 42U4 and awinding finish-side end of the neutral point-side winding section 43U4are extended to the first coil end part 40 a side (i.e., the front sideof FIG. 18), respectively forming the terminal-side and neutralpoint-side lead wires of the sub-winding U4.

Next, referring to FIG. 19, the arrangement of the 24 in-slot portionsof the fifth sub-winding U5 of the U-phase winding 41U in the ten pairsof the U-phase slots A and B will be described.

The first in-slot portion of the sub-winding U5 is arranged at the sixthlayer in the U-phase slot B of the third pole. The second in-slotportion of the sub-winding U5 is arranged at the fifth layer in theU-phase slot B of the fourth pole; the U-phase slot B of the fourth poleis away from the U-phase slot B of the third pole by six slot-pitches inthe clockwise direction.

That is, the first and second in-slot portions of the sub-winding U5 arerespectively offset from the first and second in-slot portions of thesub-winding U4 by the offset angle of 72° in the counterclockwisedirection.

Moreover, the third to the 24th in-slot portions of the sub-winding U5are arranged in the U-phase slots A and B of the stator core 30 so as tobe respectively offset from the third to the 24th in-slot portions ofthe sub-winding U4 by the offset angle of 72° in the counterclockwisedirection.

In addition, the first in-slot portion of the sub-winding U5 is includedin the terminal-side winding section 42U5 of the sub-winding U5, whilethe 24th in-slot portion of the sub-winding U5 is included in theneutral point-side winding section 43U5 of the sub-winding U5. Both awinding start-side end of the terminal-side winding section 42U5 and awinding finish-side end of the neutral point-side winding section 43U5are extended to the first coil end part 40 a side (i.e., the front sideof FIG. 19), respectively forming the terminal-side and neutralpoint-side lead wires of the sub-winding U5.

Consequently, as seen from FIGS. 14-19, all of the terminal-side andneutral point-side lead wires of the sub-windings U1-U5 of the U-phasewinding 41U are electrically connected respectively with the first and24th in-slot portions of the sub-windings U1-U5 which are arranged atthe radially outermost layer (i.e., the sixth layer in the presentembodiment) respectively in the ten U-phase slots B.

As described above, in the present embodiment, the sub-windings U1-U5 ofthe U-phase winding 41U are arranged with rotational symmetry so as tobe circumferentially offset from one another by the offset angle of 72°;the offset angle of 72° is equal to the quotient of 360° divided by thenumber of the sub-windings of the U-phase winding 41U (i.e., equal to360°/5). Moreover, in each of the U-phase slots A and B, there arearranged six of the in-slot portions 51C of the U-phase winding 41U insix layers so as to be radially aligned with each other. Furthermore,for each of the sub-windings U1-U5 of the U-phase winding 41U, thein-slot portion 51C of the sub-winding which is arranged at the Nthlayer in one of the U-phase slots A and B is electrically connected withthe in-slot portion 51C of the sub-winding which is arranged at the(N+1)th layer in another one of the U-phase slots A and B, where N is anarbitrary natural number greater than or equal to 1 and less than 6.

Moreover, in the present embodiment, as shown in FIGS. 20 and 21, foreach of the sub-windings U1-U5 of the U-phase winding 41U, the in-slotportions 51C of the sub-winding are evenly distributed to the first tothe sixth layers so that at each of the first to the sixth layers, thenumber of the in-slot portions 51C of the sub-winding received in theU-phase slots A and B is equal to 2×M, where M is the slot multipliernumber and set to 2 in the present embodiment.

More specifically, in the present embodiment, for each of thesub-windings U1-U5 of the U-phase winding 41U, the number of the in-slotportions 51C of the sub-winding arranged at the first layer in theU-phase slots A is equal to 2; the number of the in-slot portions 51C ofthe sub-winding arranged at the first layer in the U-phase slots B isequal to 2; thus the total number of the in-slot portions 51C of thesub-winding arranged at the first layer in the U-phase slots A and B isequal to 4 (i.e., 2×M with M being set to 2). Similarly, the number ofthe in-slot portions 51C of the sub-winding arranged at the second layerin the U-phase slots A is equal to 2; the number of the in-slot portions51C of the sub-winding arranged at the second layer in the U-phase slotsB is equal to 2; thus the total number of the in-slot portions 51C ofthe sub-winding arranged at the second layer in the U-phase slots A andB is equal to 4. The number of the in-slot portions 51C of thesub-winding arranged at the third layer in the U-phase slots A is equalto 2; the number of the in-slot portions 51C of the sub-winding arrangedat the third layer in the U-phase slots B is equal to 2; thus the totalnumber of the in-slot portions 51C of the sub-winding arranged at thethird layer in the U-phase slots A and B is equal to 4. The number ofthe in-slot portions 51C of the sub-winding arranged at the fourth layerin the U-phase slots A is equal to 2; the number of the in-slot portions51C of the sub-winding arranged at the fourth layer in the U-phase slotsB is equal to 2; thus the total number of the in-slot portions 51C ofthe sub-winding arranged at the fourth layer in the U-phase slots A andB is equal to 4. The number of the in-slot portions 51C of thesub-winding arranged at the fifth layer in the U-phase slots A is equalto 2; the number of the in-slot portions 51C of the sub-winding arrangedat the fifth layer in the U-phase slots B is equal to 2; thus the totalnumber of the in-slot portions 51C of the sub-winding arranged at thefifth layer in the U-phase slots A and B is equal to 4.

Moreover, in the present embodiment, as shown in FIG. 14, at each of thefirst to the sixth layers, those in-slot portions 51C of thesub-windings U1-U5 of the U-phase winding 41U which are connected withthe outer apex parts 53A (i.e., the apex parts 53A of the turn portions52A of the large electric conductor segments 50A forming thesub-windings U1-U5) are arranged alternately with those in-slot portions51C of the sub-windings U1-U5 which are connected with the inner apexparts 53B (i.e., the apex parts 53B of the turn portions 52B of thesmall electric conductor segments 50B forming the sub-windings U1-U5) inthe circumferential direction of the stator core 30.

Referring back to FIG. 5, in the present embodiment, for eachaxially-overlapping pair of the outer and inner turn portions 52A and52B, one of the outer oblique parts 55A of the outer turn portion 52Aand one of the inner oblique parts 55B of the inner turn portion 52B(i.e., the right-side outer oblique part 55A and the right-side inneroblique part 55B in FIG. 5) are in contact with each other over at leastparts of the circumferential lengths thereof. In addition, the remainingpart of the outer turn portion 52A which is out of contact with theinner oblique part 55B of the inner turn portion 52B is in contact withone of the inner oblique parts 55B of another inner turn portion 52B(not shown).

In the present embodiment, as shown in FIGS. 22 and 23, theterminal-side winding sections 42U, 42V and 42W and neutral point-sidewinding sections 43U, 43V and 43W of the U-phase, V-phase and W-phasewindings 41U, 41V and 41W (more specifically, the terminal-side windingsections 42U1-42U5, 42V1-42V5 and 42W1-42W5 and neutral point-sidewinding sections 43U1-43U5, 43V1-43V5 and 43W1-43W5 of the sub-windingsU1-U5, V1-V5 and W1-W5 of the U-phase, V-phase and W-phase windings 41U,41V and 41W) of the stator coil 40 are arranged at the radiallyoutermost layer (i.e., the sixth layer in the present embodiment) inevery M slots 31 of the stator core 30, where M is the slot multipliernumber and set to 2 in the present embodiment. That is, theterminal-side winding sections 42U, 42V and 42W and neutral point-sidewinding sections 43U, 43V and 43W of the U-phase, V-phase and W-phasewindings 41U, 41V and 41W of the stator coil 40, which respectively formthe terminal-side and neutral point-side lead wires of the U-phase,V-phase and W-phase windings 41U, 41V and 41W, are circumferentiallyspaced from one another by M slot-pitches (i.e., two slot-pitches in thepresent embodiment).

Moreover, in the present embodiment, the total number Q of theterminal-side winding sections 42U, 42V and 42W and neutral point-sidewinding sections 43U, 43V and 43W of the U-phase, V-phase and W-phasewindings 41U, 41V and 41W of the stator coil 40 (or the total number Qof the terminal-side and neutral point-side lead wires of the U-phase,V-phase and W-phase windings 41U, 41V and 41W) is set to 30.Consequently, as shown in FIG. 24, the terminal-side winding sections42U, 42V and 42W and neutral point-side winding sections 43U, 43V and43W of the U-phase, V-phase and W-phase windings 41U, 41V and 41W of thestator coil 40 are circumferentially arranged at equal angular intervalsof 12° (i.e., 360°/Q with Q being equal to 30).

Furthermore, in the present embodiment, as shown in FIG. 25, each of theneutral point-side winding sections 43U, 43V and 43W of the U-phase,V-phase and W-phase windings 41U, 41V and 41W is arranged between onecircumferentially-adjacent pair of the terminal-side winding sections42U, 42V and 42W of the U-phase, V-phase and W-phase windings 41U, 41Vand 41W. In other words, the neutral point-side winding sections 43U,43V and 43W of the U-phase, V-phase and W-phase windings 41U, 41V and41W are arranged alternately with the terminal-side winding sections42U, 42V and 42W of the U-phase, V-phase and W-phase windings 41U, 41Vand 41W in the circumferential direction of the stator core 30.Consequently, those of the terminal-side and neutral point-side leadwires of the U-phase, V-phase and W-phase windings 41U, 41V and 41Wwhich are joined by welding to the same one of the U-phase, V-phase,W-phase and neutral busbars 61-64 are not circumferentially adjacent toeach other. As a result, sufficient creepage distances are securedbetween electrical joints (or welds) 46 formed between the terminal-sideand neutral point-side lead wires and the busbars 61-64.

In the present embodiment, the terminal-side winding sections 42U of theU-phase winding 41U (more specifically, the terminal-side windingsections 42U1-42U5 of the sub-windings U1-U5 of the U-phase winding 41U)are electrically connected to the inverter via the U-phase busbar 61.Similarly, the terminal-side winding sections 42V of the V-phase winding41V (more specifically, the terminal-side winding sections 42V1-42V5 ofthe sub-windings V1-V5 of the V-phase winding 41V) are electricallyconnected to the inverter via the V-phase busbar 62. The terminal-sidewinding sections 42W of the W-phase winding 41W (more specifically, theterminal-side winding sections 42W1-42W5 of the sub-windings W1-W5 ofthe W-phase winding 41W) are electrically connected to the inverter viathe W-phase busbar 63. Moreover, all of the neutral point-side windingsections 43U of the U-phase winding 41U (more specifically, the neutralpoint-side winding sections 43U1-43U5 of the sub-windings U1-U5 of theU-phase winding 41U), the neutral point-side winding sections 43V of theV-phase winding 41V (more specifically, the neutral point-side windingsections 43V1-43V5 of the sub-windings V1-V5 of the V-phase winding 41V)and the neutral point-side winding sections 43W of the W-phase winding41W (more specifically, the neutral point-side winding sections43W1-43W5 of the sub-windings W1-W5 of the W-phase winding 41W) areelectrically connected, via the neutral busbar 64, to define the neutralpoint therebetween. In addition, the U-phase, V-phase, W-phase andneutral busbars 61-64 are electrically connected to those in-slotportions 51C of the U-phase, V-phase and W-phase windings 41U, 41V and41W of the stator coil 40 which are arranged at the radially outermostlayer (i.e., in the sixth layer in the present embodiment) in every Mslots 31 of the stator core 30, where M is the slot multiplier numberand set to 2 in the present embodiment.

Referring back to FIG. 2, in the present embodiment, each of theU-phase, V-phase, W-phase and neutral busbars 61-64 is formed of anelectrically conductive material into a predetermined arc shape.Moreover, the U-phase, V-phase, W-phase and neutral busbars 61-64 arearranged above the back core 33 of the stator core 30 so as to surroundthe first coil end part 40 a of the stator coil 40 from the radiallyoutside.

More specifically, as shown in FIG. 26, the U-phase, V-phase, W-phaseand neutral busbars 61-64 are located axially outside the stator core 30and radially outside the first coil end part 40 a of the stator coil 40which protrudes from the first axial end face 30 a of the stator core30, and arranged in axial alignment with each other. Moreover, among thefour busbars 61-64, the neutral busbar 64 which has the lowest electricpotential is located closest to the stator core 30. In addition, theneutral busbar 64 is located away from the first coil end face 30 a ofthe stator core 30 by a predetermined distance L3. Consequently, itbecomes possible to reduce the potential difference to ground, therebypreventing occurrence of a ground fault.

Furthermore, in the present embodiment, the neutral busbar 64 is set tohave a lower electric current density than the U-phase, V-phase andW-phase busbars 61, 62 and 63. Specifically, when the input current isequal to, for example, 5 A, the maximum current flowing in the U-phasebusbar 61 is equal to 2 A, as shown in FIG. 27. Similarly, though notshown in the figures, the maximum current flowing in the V-phase busbar62 and the maximum current flowing in the W-phase busbar 63 are alsoequal to 2 A. In contrast, as shown in FIG. 28, the maximum currentflowing in the neutral busbar 64 is equal to 1 A. Therefore, it is onlynecessary for the cross-sectional area of the neutral busbar 64 to begreater than 50% of the cross-sectional area of each of the U-phase,V-phase and W-phase busbars 61, 62 and 63.

In the present embodiment, as shown in FIGS. 29 and 30, the electricaljoints (or welds) 46 formed between the terminal-side winding sections42U, 42V and 42W and neutral point-side winding sections 43U, 43V and43W of the U-phase, V-phase and W-phase windings 41U, 41V and 41W andthe U-phase, V-phase, W-phase and neutral busbars 61-64 are covered byan electrically-insulative resin covering member 47 that is formed bypowder coating. The coverage range of the resin covering member 47 isset to be axially outside the axial height H of the first coil end part40 a of the stator coil 40 which protrudes from the first axial end face30 a of the stator core 30. Consequently, there is formed a spacebetween the outer apex parts 53A of the first coil end part 40 a of thestator coil 40 and the resin covering member 47.

As shown in FIGS. 31-33, the bridging wires 45 are arranged radiallyinside and axially outside the first coil end part 40 a of the statorcoil 40; as described previously, the bridging wires 45 are providedrespectively at the winding-back positions in the sub-windings U1-U5,V1-V5 and W1-W5 of the U-phase, V-phase and W-phase windings 41U, 41Vand 41W of the stator coil 40. Each of the bridging wires 45 has a pairof axially-extending portions 45 a and a circumferentially-extendingportion 45 b formed between the pair of axially-extending portions 45 a.All of the bridging wires 45 are arranged so that thecircumferentially-extending portions 45 b of the bridging wires 45overlap one another over the entire circumferential range of the firstcoil end part 40 a of the stator coil 40.

Moreover, as shown in FIG. 33, each overlapping pair of thecircumferentially-extending portions 45 b of the bridging wires 45 arefixed together by a fixing member 48. Furthermore, as shown in FIG. 31,the circumferentially-extending portions 45 b of the bridging wires 45are located at substantially the same axial position as the electricaljoints 46. In addition, each of the electrical joints 46 is formed bywelding (or alternatively by crimping) at least two electric conductorwires 57 a and 57 b radially aligned with each other.

Each of the bridging wires 45 and the electric conductor wires 57forming the electrical joints 46 has a substantially rectangular crosssection (see FIG. 6). Moreover, a shown in FIG. 31, the bridging wires45 and the electric conductor wires 57 are arranged so that side facesof the bridging wires 45 and the electric conductor wires 57, whichcorrespond to the longer sides of the substantially rectangular crosssections of the bridging wires 45 and the electric conductor wires 57,face in the radial direction of the stator core 30.

Furthermore, in the present embodiment, as shown in FIGS. 34 and 35, foreach joined-pair of the electric conductor wires 57 a and 57 b, thecircumferential width of the radially outer electric conductor wire 57 ais set to be greater than the circumferential width of the radiallyinner electric conductor wire 57 b. Consequently, during rotation of therotor 14, the radially outer electric conductor wire 57 a as well as theradially inner electric conductor wire 57 b can be exposed to coolingair (or coolant) that flows in the centrifugal direction of the rotor14. As a result, it becomes possible to suppress the temperaturedifference between the two electric conductor wires 57 a and 57 b,thereby reducing the thermal stress induced in the electrical joint 46due to the temperature difference and preventing breakage of theelectrical joint 46.

The above-described stator 20 according to the present embodiment hasthe following advantages.

In the present embodiment, the stator 20 includes the annular statorcore 30, the three-phase stator coil 40, the U-phase, V-phase andW-phase busbars 61, 62 and 63, and the neutral busbar 64. The statorcore 30 has the slots 31 arranged in the circumferential directionthereof. The stator coil 40 is comprised of the U-phase, V-phase andW-phase windings 41U, 41V and 41W that are distributedly wound on thestator core 30 so as to be different in electrical phase from eachother. Each of the phase windings 41U-41W includes the in-slot portions51C each of which is received in one of the slots 31 of the stator core30. Each of the U-phase, V-phase and W-phase busbars 61, 62 and 63 isprovided to electrically connect a corresponding one of the U-phase,V-phase and W-phase windings 41U, 41V and 41W to the inverter (i.e., anexternal electrical device). The neutral busbar 64 is provided tostar-connect the phase windings 41U-41W of the stator coil 40 to definethe neutral point therebetween. In each of the slots 31 of the statorcore 30, there are arranged K of the in-slot portions 51C of the phasewindings 41U-41W of the stator coil 40 in K layers so as to be radiallyaligned with each other, where K is an even number and set to 6 in thepresent embodiment. The number of the slots 31 formed in the stator core30 per magnetic pole of the rotor 14 and per phase of the stator coil 40is set to M, where M is a natural number greater than or equal to 2 andset to 2 in the present embodiment. Each of the phase windings 41U-41Wof the stator coil 40 is comprised of the sub-windings U1-U5, V1-V5 orW1-W5 that are connected parallel to each other. For each of thesub-windings, the in-slot portion 51C of the sub-winding which isarranged at the Nth layer in one of the slots 31 of the stator core 30is electrically connected with the in-slot portion 51C of thesub-winding which is arranged at the (N+1)th layer in another one of theslots 31, where N is an arbitrary natural number greater than or equalto 1 and less than K (i.e., less than 6 in the present embodiment). TheU-phase, V-phase, W-phase and neutral busbars 61-64 are electricallyconnected with those in-slot portions 51C of the phase windings 41U-41Wof the stator coil 40 which are arranged at the radially outermost layer(i.e., in the sixth layer in the present embodiment) in the respectiveslots 31 of the stator core 30 so as to be circumferentially spaced fromone another by M slot-pitches or more (more particularly, by twoslot-pitches in the present embodiment; see FIG. 22).

With the above configuration, it becomes possible to arrange theelectrical joints 46 formed between the U-phase, V-phase, W-phase andneutral busbars 61-64 and the phase windings 41U-41W of the stator coil40 so as to be circumferentially spaced from one another by Mslot-pitches or more. Consequently, it becomes possible to securesufficient creepage distances between the electrical joints 46, therebypreventing creeping discharge from occurring therebetween. As a result,it becomes possible to improve the insulation properties of the stator20.

Moreover, in the present embodiment, each of the sub-windings U1-U5,V1-V5 and W1-W5 of the phase windings 41U-41W of the stator coil 40includes the terminal-side winding section 42U, 42V or 42W electricallyconnected with a corresponding one of the U-phase, V-phase and W-phasebusbars 61-63, the neutral point-side winding section 43U, 43V or 43Welectrically connected with the neural busbar 64, and the main windingsection 44U, 44V or 44W between the terminal-side and neutral point-sidewinding sections. All of the terminal-side and neutral point-sidewinding sections 42U-42W and 43U-43W of the sub-windings U1-U5, V1-V5and W1-W5 of the phase windings 41U-41W are circumferentially arrangedat equal angular intervals of 360°/Q, where Q is the total number of theterminal-side and neutral point-side winding sections 42U-42W and43U-43W of the sub-windings U1-U5, V1-V5 and W1-W5 of the phase windings41U-41W and set to 30 in the present embodiment. That is, all of theterminal-side and neutral point-side lead wires of the sub-windingsU1-U5, V1-V5 and W1-W5 of the phase windings 41U-41W are circumferentialspaced from one another at equal angular intervals of 360°/Q (i.e., 12°in the present embodiment; see FIG. 24).

With the above arrangement, it becomes possible to more reliably securesufficient creepage distances between the electrical joints 46 that areformed between the terminal-side and neutral point-side lead wires ofthe sub-windings U1-U5, V1-V5 and W1-W5 of the phase windings 41U-41Wand the U-phase, V-phase, W-phase and neutral busbars 61-64. As aresult, it becomes possible to more reliably prevent creeping dischargefrom occurring between the electrical joints 46.

In the present embodiment, each of the neutral point-side windingsections 43U-43W of the sub-windings U1-U5, V1-V5 and W1-W5 of the phasewindings 41U-41W is arranged between one circumferentially-adjacent pairof the terminal-side winding sections 42U-42W of the sub-windings U1-U5,V1-V5 and W1-W5 of the phase windings 41U-41W (see FIG. 25).

With the above arrangement, it becomes possible to interpose, betweeneach pair of those electrical joints 46 which are formed between theterminal-side winding sections 42U-42W and the U-phase, V-phase andW-phase busbars 61-63 and thus have a higher electric potential, one ofthose electrical joints 46 which are formed between the neutralpoint-side winding sections 43U-43W and the neutral busbar 64 and thushave a lower electric potential. Consequently, it becomes possible tomore reliably secure sufficient creepage distances between theelectrical joints 46, thereby more reliably preventing creepingdischarge from occurring therebetween.

In the present embodiment, the electrical joints 46 formed between theterminal-side and neutral point-side winding sections 42U-42W and43U-43W of the sub-windings U1-U5, V1-V5 and W1-W5 of the phase windings41U-41W and the U-phase, V-phase, W-phase and neutral busbars 61-64 arecovered by the electrically-insulative resin covering member 47. Thestator coil 40 has the first coil end part 40 a protruding from thefirst axial end face 30 a of the stator core 30. The coverage range ofthe resin covering member 47 is axially outside the first coil end part40 a of the stator coil 40 (see FIGS. 30-31).

With the above configuration, it becomes possible to prevent thecreepage distances between the electrical joints 46 from beingshort-circuited due to adherence of the resin covering member 47 to thefirst coil end part 40 a of the stator coil 40. Consequently, it becomespossible to more reliably prevent creeping discharge from occurringbetween the electrical joints 46.

In the present embodiment, the electrical joints 46 are located axiallyoutside the first coil end part 40 a of the stator coil 40. The statorcoil 40 includes the bridging wires 45 each of which electricallyconnects one pair of the in-slot portions 51C of the phase windings41U-41W of the stator coil 40 respectively received in two differentones of the slots 31 of the stator core 30. The bridging wires 45 arelocated axially outside the first coil end part 40 a of the stator coil40 and radially inside the electrical joints 46 (see FIG. 31). Each ofthe bridging wires 45 has the pair of axially-extending portions 45 aand the circumferentially-extending portion 45 b between the pair ofaxially-extending portions 45 a. The bridging wires 45 are arranged sothat the circumferentially-extending portions 45 b of the bridging wires45 overlap one another over the entire circumferential range of thefirst coil end part 40 a of the stator coil 40 (see FIG. 32).

With the above arrangement, during rotation of the rotor 14, cooling air(or coolant) that flows in the centrifugal direction of the rotor 14 isblocked by the bridging wires 45; thus, the electrical joints 46 areprevented from being directly exposed to the flow of the cooling air.Consequently, it becomes possible to reduce thermal stress induced byuneven temperature in the electrical joints 46, thereby preventingbreakage of the electrical joints 46. As a result, it becomes possibleto improve the insulation properties of the stator 20.

In the present embodiment, the circumferentially-extending portions 45 bof the bridging wires 45 are located at substantially the same axialposition as the electrical joints 46 (see FIG. 31).

With the above arrangement, it becomes possible for the bridging wires45 to more effectively block the cooling air, thereby more reliablypreventing the electrical joints 46 from being directly exposed to theflow of the cooling air.

In the present embodiment, each of the bridging wires 45 has thesubstantially rectangular cross section and is arranged so that the pairof side faces of the bridging wire 45, which correspond to the longersides of the substantially rectangular cross sections, face in theradial direction of the stator core 30 (see FIG. 31).

With the above arrangement, it becomes possible to increase the coolingair-blocking area of the bridging wires 45, thereby more reliablypreventing the electrical joints 46 from being directly exposed to theflow of the cooling air.

In the present embodiment, each of the electrical joints 46 is formed,by welding or crimping, between one pair of the electric conductor wires57 a and 57 b radially aligned with each other. The circumferentialwidth of the radially outer electric conductor wire 57 a is set to begreater than the circumferential width of the radially inner electricconductor wire 57 b (see FIGS. 34-35).

With the above configuration, the radially outer electric conductor wire57 a as well as the radially inner electric conductor wire 57 b can beexposed to the flow of the cooling air. Consequently, it becomespossible to suppress the temperature difference between the two electricconductor wires 57 a and 57 b, thereby reducing the thermal stressinduced in the electrical joint 46 due to the temperature difference andpreventing breakage of the electrical joint 46. As a result, it becomespossible to improve the insulation properties of the stator 20.

In the present embodiment, each overlapping pair of thecircumferentially-extending portions 45 b of the bridging wires 45 arefixed together by the fixing member 48 (see FIG. 33).

With the above configuration, it becomes possible to increase thestrength of the bridging wires 45 against the flow of the cooling air,thereby reliably preventing the bridging wires 45 from being deformed oreven damaged by the flow of the cooling air. Consequently, it becomespossible for the bridging wires 45 to more reliably block the coolingair, thereby more reliably preventing the electrical joints 46 frombeing directly exposed to the flow of the cooling air.

In the present embodiment, the U-phase, V-phase, W-phase and neutralbusbars 61-64 are located axially outside the stator core 30 andradially outside the first coil end part 40 a of the stator coil 40.Moreover, the U-phase, V-phase, W-phase and neutral busbars 61-64 arearranged in axial alignment with each other. Among the U-phase, V-phase,W-phase and neutral busbars 61-64, the neutral busbar 64, which has thelowest electric potential, is located closest to the stator core 30 (seeFIG. 26).

With the above arrangement, it becomes possible to reduce the potentialdifference to ground, thereby preventing occurrence of a ground fault.As a result, it becomes possible to improve the insulation properties ofthe stator 20.

In the present embodiment, the neutral busbar 64 is set to have a lowerelectric current density than the U-phase, V-phase and W-phase busbars61, 62 and 63.

In general, with increase in the ambient temperature, it becomes easierfor electrical discharge to occur in the stator 20 and for theinsulation properties of the stator 20 to be lowered due to thermaldeterioration of the insulating members such as the resin coveringmember 47. However, by arranging the neutral busbar 64 to be closest tothe stator core 30 and lowering the electric current density of theneutral busbar 64, it is still possible to reliably prevent occurrenceof electrical discharge to the stator core 30 (or to ground). As aresult, it is still possible to reliably ensure the insulationproperties of the stator 20.

Second Embodiment

A stator 20A according to a second embodiment has almost the samestructure as the stator 20 according to the first embodiment.Accordingly, only the differences therebetween will be describedhereinafter.

As shown in FIGS. 36 and 37, in the stator 20A according to the presentembodiment, the U-phase, V-phase, W-phase and neutral busbars 61-64 areintegrated by a resin member 66 into one piece. In other words, theU-phase, V-phase, W-phase and neutral busbars 61-64 and the resin member66 together form one integrated body.

In addition, as in the first embodiment, the U-phase, V-phase, W-phaseand neutral busbars 61-64 are located axially outside the stator core 30and radially outside the first coil end part 40 a of the stator coil 40.The U-phase, V-phase, W-phase and neutral busbars 61-64 are axiallyaligned with each other. Among the U-phase, V-phase, W-phase and neutralbusbars 61-64, the neutral busbar 64, which has the lowest electricpotential, is located closest to the stator core 30.

In the present embodiment, the resin member 66 is formed, by resinmolding, so as to cover the surfaces of the U-phase, V-phase, W-phaseand neutral busbars 61-64 that are arranged in axial alignment with eachother. The resin member 66 has a cross section whose outline issubstantially rectangular in shape. The resin member 66 is arranged,together with the U-phase, V-phase, W-phase and neutral busbars 61-64embedded therein, so that a side surface of the resin member 66 abutsthe first axial end face 30 a of the stator core 30.

With the above arrangement, a ground fault (or electrical discharge toground) may occur between the busbars 61-64 and the stator core 30through voids and/or cracks formed in the resin member 66. However, asdescribed above, in the present embodiment, among the busbars 61-64, theneutral busbar 64, which has the lowest electric potential, is locatedclosest to the stator core 30. Consequently, it is still possible toreliably prevent a ground fault from occurring between the side surfaceof the resin member 66 and the first axial end face 30 a of the statorcore 30.

The stator 20A according to the present embodiment has the sameadvantages as the stator 20 according to the first embodiment.

Moreover, in the present embodiment, since the U-phase, V-phase, W-phaseand neutral busbars 61-64 are integrated by the resin member 66 into onepiece, the mechanical strength and the resistance to vibration of thestator 20A is enhanced. In addition, with the U-phase, V-phase, W-phaseand neutral busbars 61-64 embedded in the resin member 66, theinsulation properties of the stator 20A is also improved.

[First Modification]

In this modification, as shown in FIG. 38, the resin member 66 is formedby multi-phase (or multi-shot) molding to include three segments 66A,66B and 66B.

Moreover, a boundary between the segments 66A and 66B of the resinmember 66 is located on that side surface of the resin member 66 whichfaces and abuts the first axial end face 30 a of the stator core 30.

With the above arrangement, a ground fault may occur between the busbars61-64 and the stator core 30 through the boundary between the segments66A and 66B of the resin member 66. However, in the presentmodification, among the busbars 61-64, the neutral busbar 64, which hasthe lowest electric potential, is located closest to the stator core 30.Consequently, though the boundary between the segments 66A and 66B ofthe resin member 66 is located on the side surface of the resin member66, it is still possible to reliably prevent a ground fault fromoccurring between the busbars 61-64 and the stator core 30.

[Second Modification]

In this modification, as shown in FIG. 39, the resin member 66 is formedby assembling a pair of segments 66A and 66B to each other.

Moreover, a boundary between the segments 66A and 66B of the resinmember 66 is located on that side surface of the resin member 66 whichfaces and abuts the first axial end face 30 a of the stator core 30.

With the above arrangement, a ground fault may occur between the busbars61-64 and the stator core 30 through the boundary between the segments66A and 66B of the resin member 66. However, in the presentmodification, among the busbars 61-64, the neutral busbar 64, which hasthe lowest electric potential, is located closest to the stator core 30.Consequently, though the boundary between the segments 66A and 66B ofthe resin member 66 is located on the side surface of the resin member66, it is still possible to reliably prevent a ground fault fromoccurring between the busbars 61-64 and the stator core 30.

[Third Modification]

In this modification, as shown in FIG. 40, the resin member 66 is fixedto the first axial end face 30 a of the stator core 30 by a metal pin(or metal member) 67. The metal pin 67 is partially embedded in theresin member 66 during the resin molding of the resin member 66 andpress-fitted into a hole formed in the first axial end face 40 a of thestator core 40.

With the above arrangement, a ground fault may occur between the busbars61-64 and the stator core 30 through the metal pin 67. However, in thepresent modification, among the busbars 61-64, the neutral busbar 64,which has the lowest electric potential, is located closest to thestator core 30. Consequently, through there is the metal pin 67 bridgingthe resin member 66 and the stator core 30, it is still possible toreliably prevent a ground fault from occurring between the busbars 61-64and the stator core 30.

[Fourth Modification]

In this modification, as shown in FIG. 41, the resin member 66 is fixedto the first axial end face 30 a of the stator core 30 by a metal plate(or metal member) 67. The metal plate 67 is partially embedded in theresin member 66 during the resin molding of the resin member 66 andwelded to the first axial end face 40 a of the stator core 40.

With the above arrangement, a ground fault may occur between the busbars61-64 and the stator core 30 through the metal plate 67. However, in thepresent modification, among the busbars 61-64, the neutral busbar 64,which has the lowest electric potential, is located closest to thestator core 30. Consequently, through there is the metal plate 67bridging the resin member 66 and the stator core 30, it is stillpossible to reliably prevent a ground fault from occurring between thebusbars 61-64 and the stator core 30.

While the above particular embodiments and their modifications have beenshown and described, it will be understood by those skilled in the artthat the present invention can also be embodied in various other modeswithout departing from the spirit of the present invention.

For example, in the above-described embodiments, all of theterminal-side and neutral point-side lead wires of the phase windings41U-41W of the stator coil 40 are respectively led from those in-slotportions 51C of the phase windings 41U-41W which are arranged at theradially outermost layer (i.e., in the sixth layer in theabove-described embodiments) in the respective slots 31 of the statorcore 30 so as to be circumferentially spaced from one another by Mslot-pitches or more. That is, the U-phase, V-phase, W-phase and neutralbusbars 61-64 are electrically connected with those in-slot portions 51Cof the phase windings 41U-41W which are arranged at the radiallyoutermost layer in the respective slots 31 of the stator core 30 so asto be circumferentially spaced from one another by M slot-pitches ormore.

However, all of the terminal-side and neutral point-side lead wires ofthe phase windings 41U-41W of the stator coil 40 may be respectively ledfrom those in-slot portions 51C of the phase windings 41U-41W which arearranged at the radially innermost layer (i.e., in the first layer inthe above-described embodiments) in the respective slots 31 of thestator core 30 so as to be circumferentially spaced from one another byM slot-pitches or more. That is, the U-phase, V-phase, W-phase andneutral busbars 61-64 may be electrically connected with those in-slotportions 51C of the phase windings 41U-41W which are arranged at theradially innermost layer in the respective slots 31 of the stator core30 so as to be circumferentially spaced from one another by Mslot-pitches or more.

In the above-described embodiments, the stator coil 40 is distributedlywave-wound on the stator core 30. However, the stator coil 40 may alsobe distributedly lap-wound on the stator core 30.

In the above-described embodiments, the present invention is directed tothe stator 20 or 20A of the rotating electric machine 1 that is designedto be used in a motor vehicle as an electric motor. However, the presentinvention can also be applied to stators of other rotating electricmachines, such as a stator of an electric generator or a stator of amotor-generator that can selectively function either as an electricmotor or as an electric generator.

What is claimed is:
 1. A stator for a rotating electric machine, thestator comprising: an annular stator core having a plurality of slotsarranged in a circumferential direction thereof; and a stator coilcomprised of a plurality of phase windings that are distributedly woundon the stator core, each of the phase windings including a plurality ofin-slot portions each of which is received in one of the slots of thestator core, wherein the stator coil has an annular coil end partprotruding from an axial end face of the stator core, there areelectrical joints formed for making electrical connection of the statorcoil and covered by an electrically-insulative resin covering member,the electrical joints being located axially outside the coil end part ofthe stator coil, the stator coil includes a plurality of bridging wireseach of which electrically connects one pair of the in-slot portions ofthe phase windings of the stator coil respectively received in twodifferent ones of the slots of the stator core, the bridging wires beinglocated axially outside the coil end part of the stator coil andradially inside the electrical joints, each of the bridging wires has apair of axially-extending portions and a circumferentially-extendingportion between the pair of axially-extending portions, and the bridgingwires are arranged so that the circumferentially-extending portions ofthe bridging wires overlap one another over an entire circumferentialrange of the coil end part of the stator coil.
 2. The stator as setforth in claim 1, wherein the circumferentially-extending portions ofthe bridging wires are located at substantially a same axial position asthe electrical joints.
 3. The stator as set forth in claim 1, whereineach of the bridging wires has a substantially rectangular cross sectionand is arranged so that a pair of side faces of the bridging wire, whichcorrespond to longer sides of the substantially rectangular crosssections, face in a radial direction of the stator core.
 4. The statoras set forth in claim 1, wherein each of the electrical joints isformed, by welding or crimping, between one pair of electric conductorwires radially aligned with each other, and a circumferential width of aradially outer electric conductor wire is set to be greater than acircumferential width of a radially inner electric conductor wire. 5.The stator as set forth in claim 1, wherein each overlapping pair of thecircumferentially-extending portions of the bridging wires are fixedtogether by a fixing member.